A normal July in the tropics?

By: Dr. Jeff Masters , 1:56 PM GMT on July 10, 2006

Share this Blog
0
+

A tropical wave about 900 miles east of the Lesser Antilles Islands has become much less organized since this morning. Strong upper-level winds just to the system's north have disrupted it, and its west-northwestward track should take it deeper into this area of high shear. I don't expect any development from this wave. There is some deep thunderstorm activity to the southwest of this wave, near 9N 52W, that is not undergoing as much shear. However, this area is disorganized, and I don't expect any development here, either.

The other area of interest today and a large area of deep thunderstorms stretching from Puerto Rico to the southeastern Bahama Islands. These showers are associated with a cold-cored upper-level low pressure system that is moving slowing west-northwestward. Any development of this area will be slow, due to wind shear, high surface pressures, and dry air. This disturbance should move over Florida on Wednesday, bringing heavy rain to portions of the state.


Figure 1. Latest satellite image of the tropical wave approaching the Lesser Antilles Islands.


Figure 1. Model forecast tracks for the tropical wave approaching the Lesser Antilles Islands.

A normal July?
Will July 2006 be a normal July for the Atlantic hurricane season? First, we need to look at what constitutes a normal July. As we can see from the Atlantic hurricane frequency graph in Figure 3, July is typically a very quiet month, almost as quiet as June is. It's usually not until the second week of August that hurricane season really starts to heat up. Since the current active Atlantic hurricane period began in 1995, there have been an average of about 1.5 named storms and 0.8 hurricanes per July. It's common to go several years in a row without getting a July tropical storm, as happened in 1999-2001. Last year's five named storms in July--including three hurricanes, two of them major hurricanes--was definitely an extremely unusual year. By this time last year, we were already on our fourth named storm, and Category 4 Hurricane Dennis was churning its way through the Caribbean.


Figure 3. The curve of historical normal hurricane activity of the Atlantic Ocean.

Why is July usually so quiet?
Sea Surface Temperatures right now (Figure 4) are warm enough to support tropical storm formation throughout the Gulf of Mexico, Bahamas, and the Main Development Region (MDR) of the Atlantic (the MDR is the region between 10N and 20N, and includes the Caribbean Sea). The only part of the MDR still too cool to support tropical storms is the far eastern Atlantic off the coast of Africa. SSTs generally do not get warm enough to support the classic intense "Cape Varde" hurricanes that form off the coast of Africa until mid-August in this region. Thus, we should not expect any Cape Verdes type hurricanes until August.


Figure 4. Atlantic SSTs for July 4, 2006. Blue colors represent SSTs colder than 26 C (80 F), which are too cool to support tropical storm formation.

Since SSTs are not the limiting factor, our old friend wind shear must be the answer! Let's look at wind shear in the eastern Caribbean, where both Hurricane Dennis and Hurricane Emily intensified into major hurricanes last year. As we can see from Figure 5, wind shear was very low in this region in 2005, and has been near normal or even above normal in 2006. Wind shear is expected to remain near average or above average across the the entire tropical Atlantic for the remainder of this week. While it is possible a tropical storm could form in a "hole" in the wind shear, the chances of it being able to stay together for an extended period and grow into a hurricane are low. So, it appears that the first half of July is shaping up to be a very normal one in the tropics.

What about the last half of July?
The two-week forecast from the GFS computer model has been consistently predicting a steady reduction in the amount of wind shear over the tropical Atlantic for the week of July 15 - July 23. Thus, many more "holes" in the wind shear will be opening up, potentially allowing tropical storms to form. I'll stick with my prediction I made at the end of June that we'll see one or two named storms in July, one of which may be a hurricane (but not a major hurricane). The forecast pressure pattern for the rest of July continues to show a weakness in the Bermuda High near the U.S. East Coast. This favors an above-normal chance of strikes on the U.S. East Coast, and a below-normal chance for the Gulf Coast, for storms forming in the Caribbean or near the Bahama Islands.


Figure 5. Wind shear over the Eastern Caribbean in 2005 (red line) and 2006 (blue line) compared to normal (black line). Wind shear is computed as the difference in wind between the upper atmosphere (200 mb pressure, about 40,000 feet high) and lower atmosphere (850 mb pressure, about 5,000 feet high). Image credit: CIRA

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 722 - 672

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15Blog Index

721. K8eCane
2:11 PM GMT on July 11, 2006
thanks guy
Member Since: April 26, 2006 Posts: 5 Comments: 3098
720. Buhdog
2:11 PM GMT on July 11, 2006
I could not have said that any better Guygee...
really...pretty wild having those two big eyes looking at us on both sides of FL.....
Member Since: July 30, 2005 Posts: 1 Comments: 960
719. K8eCane
2:10 PM GMT on July 11, 2006
LOL red mosquito
if we are such dummies on here why would he waste his time
he would be better off to stand by his fax machine because he must get lots of questions
Member Since: April 26, 2006 Posts: 5 Comments: 3098
718. guygee
2:08 PM GMT on July 11, 2006
The terminology is a little ambiguous at times, but a closed upper level low or a low-pressure trough that forms in the easterlies is usually referred to as a TUTT. A "cut-off" low is usually the term used to refer to an upper-level low that forms in the westerlies and then gets "cut-off" from the westerlies as the westerlies shift north or the upper-level low sinks south. The ambiguity is shown by the ULL currently in the eastern Gulf. It was originally formed by at base of the trough being pushed by the prevailing westerlies farther north, but it dropped south and got "cut-off" from the westerlies. Now it is getting embedded in the easterlies as the high builds to the north.

In any event, both the terms "cut-off low" and "TUTT" refer to an upper-level cold core area of low pressure, it is just a matter of the origin of the upper-level low.
Member Since: September 16, 2005 Posts: 0 Comments: 3148
717. IKE
2:06 PM GMT on July 11, 2006
Which way does Bastardi think it would move?

He use to be on Florida Network News, but apparently isn't anymore...miss hearing his opinion.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
716. RedMosquito
2:05 PM GMT on July 11, 2006
STORMOP: WHILE I SIT BACK AND LAUGH.

715. hurricane23
2:05 PM GMT on July 11, 2006
my concern for the wave near the bahamas has grown a little this morning.currently waiting jb's update on the wave...He seems interested in possible development east of florida.
Member Since: May 14, 2006 Posts: 8 Comments: 13676
714. thelmores
1:53 PM GMT on July 11, 2006
looks like business is picking up on the bahamas radar

gonna be a stormy couple days in south florida it appears........
Member Since: September 8, 2005 Posts: 0 Comments: 3805
713. K8eCane
1:49 PM GMT on July 11, 2006
thanks skyepony
Member Since: April 26, 2006 Posts: 5 Comments: 3098
712. Skyepony (Mod)
1:47 PM GMT on July 11, 2006
NHC is calling it an ULL. Lastnight they called it a cut off low. Yesterday ULL. They always mentioned caught up in that dying trough. Your right a TUTT is nothing more than an ULL caught in a trough. To refure to it as an ULL shouldn't be a big deal since that is how the NHC does. They mention the trough, but they mention every feature out there. I've yet to see them call this a TUTT, thought it is described as such. Using the NHC disscussion's terminalogy as my source, I agree, you were unfairly attacked yesterday.
Member Since: August 10, 2005 Posts: 162 Comments: 37782
711. snotly
1:41 PM GMT on July 11, 2006
yea they better loosen up or I'm going to send my lightning bolts and storm clouds to teach them a lesson
Member Since: August 27, 2005 Posts: 0 Comments: 683
710. K8eCane
1:33 PM GMT on July 11, 2006
people do have their control issues
some actually think they can control the weather
Member Since: April 26, 2006 Posts: 5 Comments: 3098
709. K8eCane
1:32 PM GMT on July 11, 2006
are you really calling this an ULL now? i was disagreed with yesterday on that terminology
Member Since: April 26, 2006 Posts: 5 Comments: 3098
707. K8eCane
1:30 PM GMT on July 11, 2006
stormtop
do you not have better things to do than just sit back and laugh at a bunch of people on a blog?
you need help man
unless its your blog
Member Since: April 26, 2006 Posts: 5 Comments: 3098
706. snotly
1:28 PM GMT on July 11, 2006
that 96I flare up looks like a fish. Should we call it the fish blob
Member Since: August 27, 2005 Posts: 0 Comments: 683
705. K8eCane
1:28 PM GMT on July 11, 2006
doesnt look like weakening to me
looks like its tightening
ULL off east coast
Member Since: April 26, 2006 Posts: 5 Comments: 3098
703. Skyepony (Mod)
1:12 PM GMT on July 11, 2006
Here's the link to the discussion (that's a partial post of it). Weather is ominous here this morning.
Member Since: August 10, 2005 Posts: 162 Comments: 37782
702. thelmores
1:10 PM GMT on July 11, 2006
i hope i never see a 100ft rogue wave either! LOL
Member Since: September 8, 2005 Posts: 0 Comments: 3805
701. Skyepony (Mod)
1:09 PM GMT on July 11, 2006
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE JUL 11 2006

TROPICAL WAVE IS ALONG 49W S OF 15N MOVING W 10-15 KT WITH A
1013 MB LOW ALONG THE WAVE NEAR 12N. NEITHER WAVE OR LOW ARES
WELL DEFINED. SCATTERED MODERATE CONVECTION IS FROM 11N-13N
BETWEEN 49W-51W.

UPPER LOW IS IN THE E GULF NEAR 24N85W WITH THE UPPER TROUGH
COVERING THE AREA E OF 90W. THE DISSIPATING SURFACE TROUGH
EXTENDS FROM S GEORGIA NEAR 32N83W ACROSS THE FLORIDA PANHANDLE
TO 27N88W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM
23N-27N E OF 87W ACROSS FLORIDA INTO THE W ATLC.

A BROAD UPPER HIGH IS CENTERED NEAR 27N67W WITH UPPER RIDGE
COVERING THE ATLC FROM 60W-80W. EMBEDDED WITHIN THIS FLOW IS A
WEAKENING MID LEVEL LOW CENTERED NE OF THE N BAHAMA ISLANDS NEAR
28N75W MOVING NORTHWARD. DIFFLUENCE TO THE W OF THE UPPER RIDGE
IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 27N
FROM 69W ACROSS S FLORIDA AND THE STRAIT OF FLORIDA IN TO THE SE
GULF AND WITHIN 120 NM OF LINE FROM 27N75W TO BEYOND 32N72W.

$$
WALLACE

Member Since: August 10, 2005 Posts: 162 Comments: 37782
700. thelmores
1:06 PM GMT on July 11, 2006
hey ST, better get that keyboard checked out.... it appears your caps lock is stuck! Or is it meant to be just a childish "rant", thus caps are ok?

seems a nice "flareup" on the 96l wv loop

and, looks like another "blob" in the bahamas! LOL
Member Since: September 8, 2005 Posts: 0 Comments: 3805
699. snotly
1:05 PM GMT on July 11, 2006
I THINK THAT STORMTOPS ONLY FLAW IS TACK AND THAT HE CANT EXPRESS HIMSELF WITHOUT HAVING A CONDESCENDING TONE...

or he just forgot to undo the caps lock and needs to take his high blood pressure pills again...

Member Since: August 27, 2005 Posts: 0 Comments: 683
698. nash28
1:05 PM GMT on July 11, 2006
Good morning everyone. Looks like the shear gods have spoken again. Most definately a different start to this year as opposed to 2005.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
697. Cavin Rawlins
1:03 PM GMT on July 11, 2006
the comments are coming in..and so far no one wnats the bill to be pass...you can make a contribution at mt blog.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
696. guygee
1:03 PM GMT on July 11, 2006
Interesting article in today's NY Times online on rogue waves in the ocean.
Member Since: September 16, 2005 Posts: 0 Comments: 3148
694. Cavin Rawlins
12:32 PM GMT on July 11, 2006
AccuWeather Vs The NWS: Part 2
AccuWeather has been a vocal critic of the National Weather Service, a part of the U.S. government's NOAA, in that it provides free weather forecasting services to the general public. They argue that the government competes with them directly and unfairly, and on April 14, 2005 senator Rick Santorum introduced the "National Weather Services Duties Act of 2005" to the U.S. Senate that would prohibit the NWS from providing products or services the private sector is willing and able to provide (S. 786). The bill is currently pending.
Question: Does AccuWeather have a valid point and should the bill be pass by the US Senate?


Figure 1: My Logo of the debate between AccuWeather and the NWS

My Questions:
You can still make or update your July predictions and the question on Atlantic Multidecadal Oscillation Vs Global Warming on Hurricane Activity is still open. Also open is the question on Why was the 2005 Season more destructive that the 2004 Season even though they both had about the same number of storms making landfall. I need some more information on the two latest question to make a comprehensive conclusion/summary so you can post what ever you know.

you can leave comments ta my blog.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
693. IKE
12:31 PM GMT on July 11, 2006
*today*
Member Since: June 9, 2005 Posts: 23 Comments: 37858
692. IKE
12:27 PM GMT on July 11, 2006
One year ago toady Emily was born. What a difference a year makes.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
691. EdMahmoud
12:25 PM GMT on July 11, 2006
How cool is it that the TC in the East Pac is named 'Bud'.

'Specially since I'm a fan of the #8 car.
Member Since: October 19, 2005 Posts: 0 Comments: 398
690. IKE
12:20 PM GMT on July 11, 2006
NAM model/low is being discounted according to the Key West morning discussion.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
688. IKE
10:57 AM GMT on July 11, 2006
I reported you as being obscene TX. No place for that talk here.

Looking at the NAM and GFS models....

The NAM develops a 1016 mb low east of Florida and rides it up the east coast of Florida...strengthening it slightly to 1012 mb.

The GFS has it crossing Florida and heading into the gulf at 1016 mb...

We desperately need rain here in the Florida panhandle. Crestview has had a...trace of rain for the month...just been too dry here.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
684. Inyo
7:15 AM GMT on July 11, 2006
I was just looking today at this week's ENSO report and noticed a strong warming of waters off the west coast of Mexico to well above average. Sure enough, tonight the E-pac is firing up... the depression is only expected to reach tropical storm strength but some models predict another more intense storm to its east soon.

If current trends continue, we may end up with a more active e-pac season than expected. Hopefully this will take away from the atlantic season.
Member Since: September 3, 2002 Posts: 42 Comments: 873
683. turtlehurricane
5:40 AM GMT on July 11, 2006
Hi StormTop, were all gonna die from global warming. Thanks for the great forecast :) Night StormTop


BTW, how are the TSC levels out there?
Member Since: July 22, 2005 Posts: 227 Comments: 469
682. cjnew
5:39 AM GMT on July 11, 2006
Wrong ST...???
0000

I cant remember anything
Member Since: July 22, 2005 Posts: 84 Comments: 2779
681. cjnew
5:37 AM GMT on July 11, 2006
OH! thats the wrong ST!
or is the right?? its got the zero
Member Since: July 22, 2005 Posts: 84 Comments: 2779
678. StormThug
5:35 AM GMT on July 11, 2006
stormtop keep it gangsta but dont trip
Member Since: June 15, 2006 Posts: 9 Comments: 480
677. StormThug
5:32 AM GMT on July 11, 2006
stormtop chill dude its ight
Member Since: June 15, 2006 Posts: 9 Comments: 480
676. cjnew
5:31 AM GMT on July 11, 2006
Thanks for the Update ST!!!

DO you always switch from first to third person?

or.....
Nah! :)
G,nite~~~~
Member Since: July 22, 2005 Posts: 84 Comments: 2779
674. hurricane23
5:30 AM GMT on July 11, 2006
That's pretty bold. By chance do you have any reasoning to that or just the fact that we haven't had much development yet? If your looking to get a reaction out of people.. your probably going to get it.
Member Since: May 14, 2006 Posts: 8 Comments: 13676
672. BahaHurican
5:10 AM GMT on July 11, 2006
Anyhoo, folks,

I'm off to bed. More speculation, cogitation, and prediction tomorrow . . .

Sleep tight!
Member Since: October 25, 2005 Posts: 19 Comments: 21864

Viewing: 722 - 672

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
71 °F
Overcast